X-band modulation of GaAs lasers

This correspondence reports CW amplitude modulation of GaAs injection lasers at X band. The highest modulation frequency was 11 Gc/s, a limit imposed by components of the experimental setup. The X-band modulating signal is amplified in a traveling-wave amplifier and coupled to the laser. Two directional couplers monitor the forward and reflected RF power. The RF power is coupled to the laser in a waveguide structure. In this structure, the copper fins act as a short circuit to the X-band power while the modulated infrared radiation passes unaffected (neglecting some blockage). The laser, located between two sections of a copper post, is spaced a half guide wavelength (at 9.1 Gc/s) from the RF shortcircuiting fins.